The invention relates to halogenated phosphorus esters which contain hydroxyalkyl and t-alkoxyalkyl groups. The compounds of this invention are useful as flame retardants, or intermediates in the preparation of flame retardants, for polyurethanes.
Polyurethanes, particularly polyurethane foam plastics, find widespread uses in industry for a plurality of purposes, and they are still gaining increasing interest. Because of their excellent heat and sound-absorbing properties, polyurethane foam plastics are widely used for example, in the building industry, as heat insulator in refrigerators and cars, pipelines, tanks, tank cars, and for a plurality of further purposes. A particularly beneficial effect which polyurethanes offer is the ease with which they can be produced on the spot. Polyurethane soft plastics are widely employed in commercial quantities for the manufacture of mattresses, upholstery for furniture and automobile seats, and for many other uses.
To be suitable for these uses, it is often necessary or at least desirable for the polyurethanes to have satisfactory flame retarding properties. Various attempts have already been made to render polyurethanes flame retardant. One involves adding a phosphorus-containing flame retarding agent thereto. In those cases, however, in which these additives are merely incorporated with the plastics, they are likely to migrate or become extracted therefrom, under outdoor conditions, especially if polyurethane foam plastics are concerned. A substantial progress in flame retarding polyurethanes has been achieved through the use of phosphorus-containing polyols, which are chemically bound in polyurethanes. These polyols can be made, for example, by the additive combination of epoxides with an acid of phosphorus, or its acid esters. Phosphorus compounds having additional halogen therein are known to improve the non-inflammability of plastics as the use of phosphorus together with a halogen, which preferably is chlorine or bromine, has been found to produce a synergistic flame retarding effect.
It is commonly known that polyurethanes are produced by preparing a blend from high molecular weight compounds containing at least 2 active hydrogen atoms, and polyisocyanates in the presence of one or more catalysts and, if desired, expanding agents, surface-active substances and further auxiliaries. The compounds of high molecular weight include, for example, phosphorus- and halogen-containing polyols, which may be used alone or in combination with further customary compounds, such as polyetherpolyols, polyesterpolyols and polyester amides.
Phosphorus hydroxyalkyl esters are known in the art.
Baranauckas et al., U.S. Pat. No. 3,737,397, disclose esters of phosphonic acid containing three or more hydroxy groups, methods for the preparation thereof, and polyurethane foams having such compounds incorporated therein.
Vollmer et al., U.S. Pat. No. 3,978,170, disclose the production of polyols containing halogen and phosphorus. The polyols find use as flame retarding agents in plastics, particularly in polyurethane foams.
Wortmann et al., U.S. Pat. No. 3,850,859, disclose difficultly inflammable polyurethane foam plastics, and a process for making them with the use inter alia of a phosphorus- and chlorine-containing polyol as a flame-proofing component. The reference discloses processes for the preparation of phosphorus- and chlorine-containing polyols.
Albright, U.S. Pat. No. 4,133,846, discloses esters of pentavalent phosphorus acid and plastic compositions containing these esters as flame retardants. These esters contain halogen atoms and hydroxyl moieties.
Halogenated phosphorus compounds from which primary hydroxyl groups containing halogenated phosphorus compounds can be prepared in a controlled manner without the formation of undesirable by-products are needed. Halogenated phosphorus compounds which contain one or more reactive hydroxyl groups which have relatively high amounts of halogen incorporated therein are further needed.